Vehicles are generally equipped with audio devices that play an audio sound in a cabin. JP2776092B and JP1993-085288A disclose audio devices that perform localization of an audio sound so that a person(s) on board is able to hear the audio sound from a given position in a cabin.
Meanwhile, vehicles which are focused on the enjoyment of traveling, such as sports cars, are required to actively cause person(s) on board, especially a vehicle driver, to hear (listen to) an engine sound. That is, since the engine sound is a good indication of a vehicle state, it becomes an extremely important element in the enjoyment of traveling, and how to effectively cause the person(s) on board to hear the engine sound is important. Additionally, in order to actively cause the person(s) on board to hear the engine sound, distinguishing an audio sound from the engine sound and how to effectively cause the person(s) to hear it become important.